Mesenchymal stem cells reversibly dedifferentiate myofibroblasts to fibroblast-like cells by down-regulating the TGF-β-SMAD2/3 pathway

Bronchiolitis obliterans (BO) is a pulmonary chronic graft-versus-host disease (cGVHD), which is a noninfectious, irreversible, and poor prognostic complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Fibroblast-myofibroblast transition (FMT)-derived myofibroblasts (MFB) are the main effector cells involved in the development of BO. Through multiple regulations, the anti-fibrotic potential of mesenchymal stem cells (MSC) has been widely studied and was implied with potential clinical value. However, the MSC-mediated regulation of FMT and underlying mechanisms remained largely undefined. By identifying TGF-β1 hypertension as the pivotal landmark during the profibrotic FMT, TGF-β1-induced MFB and uMSC co-culture models were established and utilized to investigate regulations by uMSC on FMT in vitro. Methods including RNA sequencing (RNA-seq), Western blot, qPCR and flow cytometry were used. Our results revealed that uMSC reversibly dedifferentiated MFB into a group of FB-like cells by modulating the TGF-β-SMAD2/3 signaling. Importantly, these proliferation-boosted FB-like cells remained sensitive to TGF-β1 and could be re-induced into MFB. Our findings highlighted the reversibility of uMSC-mediated inhibitions on FMT through TGF-β-SMAD2/3 signaling, which may explain MSC's inconsistent clinical efficacies in treating BO and other fibrotic diseases. These dedifferentiated FB-like cells are still sensitive to TGF-β1 and may further deteriorate MFB phenotypes unless the profibrotic environment is corrected. RNA-sequencing data of untreated lung fibroblasts (FB), TGF-β1-induced myofibroblasts (MFB), and MFB co-cultured with MSCs (MFB-MSC).